Carbon-based Solid Acid Research Articles

Synthesis of sulfonated carbon-based solid acid as a novel and efficient nanocatalyst for the preparation of highly functionalized piperidines and acylals: a DFT study

A novel carbon-based solid-acid nanocatalyst (Sta-SO3H) was simply prepared for the first time by the thermal treatment of sulfuric acid with starch at 180 °C in a sealed autoclave. The catalytic activities of Sta-SO3H as an efficient and reusable catalyst were investigated by the condensation reaction of aldehyde, amine and β-keto ester for the synthesis of functionalized piperidines under solvent-free conditions at room temperature in good to high yields. Density functional theory calculations were used to study the structure of methyl 1,2,6-triphenyl-4-(phenylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate (MPPC) as well as the thermochemistry of the multicomponent reaction. The theoretically calculated infrared and 1H nuclear magnetic resonance spectra of MPPC were compared to the experimental data. It was found that the synthesis of MPPC is exothermic accompanied by a decrease in entropy, internal energy and Gibbs free energy of reaction. Good consistency between the calculated and observed spectral data was found. Also, Sta-SO3H has been developed for the synthesis of acylals (1,1-diacetate) in high yields through the reaction of aldehydes with acetic anhydride at room temperature under solvent-free conditions. The mild conditions, eco-friendliness, excellent yields, short reaction times and use of an inexpensive and reusable catalyst are important features of this method.

High-performance carbon-based solid acid prepared by environmental and efficient recycling of PVC waste for cellulose hydrolysis

Pyrolysis techniques can provide a way to convert polyvinyl chloride (PVC) waste into high value liquids and gases.

A novel highly ordered mesoporous carbon-based solid acid for synthesis of bisphenol-A

Effect of different catalysts on phenol–acetone condensation reaction.

Carbon-based acid catalyst from waste seed shells: preparation and characterization

Abstract A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized seed shells of Jatropha curcas (J. curcas L.). The structure of amorphous carbon consisting of polycyclic aromatic carbon sheets attached a high density of acidic SO3H groups (2.0 mmol · g−1) was identified with scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The performance of the solid acid catalyst was evaluated for biodiesel production in the esterification of oleic acid with methanol. 95.7% yield of biodiesel was obtained after 2 h reaction and the conversions with reused catalyst varied in the range of 95.7% to 95.1%, showing better activity and stability than commercial catalyst amberlyst-46. It was also observed that the prepared catalyst showed enhanced activity in the transesterification of triolein with methanol when compared with other solid acid catalysts. A synergistic effect results from the high density of SO3H groups and the good access of reactants to the acidic sites can be used to explain the excellent catalytic activity, as well as the strong affinity between the hydrophilic reactants and the neutral OH groups bonded to the polycyclic aromatic carbon rings.

Simple fabrication of magnetically separable mesoporous carbon sphere with excellent catalytic performance for biodiesel production

Considering the problem of separation of carbon-based powder solid acid, facile separation of solid acid shows the superiority for recycling. A novel and magnetically separable mesoporous carbon sphere (MMCS−SO3H) solid acid catalyst was prepared by sulfonation of γ-Fe2O3 nanoparticle composited mesoporous carbon sphere with organic sulfonic acid. The results of N2 adsorption–desorption technology and electron microscopy show that this MMCS−SO3H solid acid owns superior mesoporous structure and uniform spherical morphology. The solid acid possesses high acidity of 1.73 mmol H+/g and SO3H density of 1.08 mmol/g, which favor this solid acid exhibiting satisfactory catalytic property for the esterification of oleic acid. The influences of reaction temperature and molar ratio of MeOH/OA on catalytic performance of catalyst were also systematically investigated. In addition, the carbon-based solid acid exhibited excellently catalytic stability and recycling property.

SO3H-modified petroleum coke derived porous carbon as an efficient solid acid catalyst for esterification of oleic acid

A carbon-based solid acid catalyst was simply prepared from petroleum coke by chemical activation and subsequent sulfonation. The structure–function relationships of the solid acid catalyst were investigated by regulating activation temperature. The materials were characterized by nitrogen adsorption, SEM, XRD, FT-IR and element analysis. The catalytic performances of catalysts were evaluated by the esterification of oleic acid with methanol, which is a crucial reaction in the production of biodiesel. The solid acid catalyst activated at 800 °C exhibits the most excellent catalytic activity, which is attributed to its large surface area (851 m2/g) and high acid density (1.04 mmol/g). At the optimized conditions, high conversion (89.5 %) was achieved and no distinct activity drop was observed after five recycles. This work may offer a facile strategy to fabricate solid acid catalysts in large scale for green chemical processes.

Efficient dehydration of fructose to 5-hydroxymethylfurfural over sulfonated carbon sphere solid acid catalysts

A carbon-based solid acid catalyst was prepared via hydrothermal method using glucose as carbon precursors and aqueous solution of H2SO4 as sulfonation agent. The as-synthesized solid acid catalyst was attempted in the catalytic dehydration of fructose to 5-hydroxymethylfurfural (HMF). The effects of acid site density, reaction time, solvents, catalyst amount, temperature and mole ratio of catalyst to substrate were investigated. Under the optimum reaction conditions, the HMF yield of 90% was achieved in dimethylsulfoxide (DMSO) solvent at 160°C after 1.5h reaction time duration. The solid acid catalyst can be separated from the reaction mixture after reaction and reused without substantial loss in catalytic activity.

Synthesis porous carbon-based solid acid from rice husk for esterification of fatty acids

A porous carbon solid acid was synthesized from biomass rice husk by incompletely carbonization, sodium hydroxide leaching and concentrated H2SO4 sulfonation. The solid acid was characterized by XRD, FT-IR, N2 adsorption-desorption and solid-state NMR spectroscopy. The characterization results reveal that the carbon solid acid shows ultra high surface area of 1233 m2/g and stronger acid strength than that of HZSM-5(Si/Al = 38) zeolite. The catalytic performance was tested by the esterification of oleic acid with methanol. The results indicate that this solid acid catalyst is an excellent catalyst compared with other conventional solid acid.

Transesterification of Tributyrin and Dehydration of Fructose over a Carbon-Based Solid Acid Prepared by Carbonization and Sulfonation of Glucose.

A series of carbon-based sulfonated solid acid (CS) catalysts can be prepared through a facile method of direct simultaneous carbonization and sulfonation of d-glucose with concentrated sulfuric acid without a hydrothermal process. Temperature is a key factor in obtaining CS catalysts with higher amounts of -SO3 H acid sites. The transesterification of tributyrin with methanol and the dehydration of fructose to 5-hydroxymenthylfurfural (5-HMF) are investigated over the CS catalysts. The CS-150 catalyst, which is the CS catalyst prepared at 150 °C, shows much higher catalytic activity to give a tributyrin conversion of 99.4 %. The yield of methyl butyrate is 97.2 % and a remarkably high yield of 5-HMF (93 %) can be obtained efficiently; these yields result from the high acid density of -SO3 H. Good linearity is displayed between the total acid density and yield of methyl butyrate/5-HMF. The CS-150 catalyst has high stability and good recyclability for the dehydration of fructose.

Carbon-based strong solid acid for cornstarch hydrolysis

Highly sulfonated carbonaceous spheres with diameter of 100–500nm can be generated by hydrothermal carbonization of glucose in the presence of hydroxyethylsulfonic acid and acrylic acid at 180°C for 4h. The acidity of the prepared carbonaceous sphere C4-SO3H can reach 2.10mmol/g. It was used as a solid acid catalyst for the hydrolysis of cornstarch. Total reducing sugar (TRS) concentration of 19.91mg/mL could be obtained by hydrolyzing 20mg/mL cornstarch at 150°C for 6h using C4-SO3H as solid acid catalyst. The solid acid catalyst demonstrated good stability that only 9% decrease in TRS concentration was observed after five repeat uses. The as-prepared carbon-based solid acid catalyst can be an environmentally benign replacement for homogeneous catalyst.

ChemInform Abstract: An Overview on Synthetic Methods of Tributyl Citrate

AbstractReview: 8 refs.

Esterification of Free Fatty Acid on Palm Fatty Acid Distillate using Activated Carbon Catalysts Generated from Coconut Shell

In the last few years, biodiesel has emerged as one of the most potential renewable energy to replace current petrol-derived diesel. It is a renewable, biodegradable and non-toxic fuel which can be easily produced through esterification of triglycerides (vegetable oils or animal fats) or esterification of free fatty acids (FFAs) with methanol. However, current commercial usage of refined vegetable oils for biodiesel production is impractical and uneconomical due to high feedstock cost and priority as food resources. Low-grade oil, can be a better alternative; however, the high free fatty acids (FFA) content has become the main drawback for this potential feedstock. Solid acid catalysts offer significant advantages of eliminating separation, corrosion, toxicity and environmental problems. Recently, a new strategy of preparing novel carbon-based solid acids has been developed. In this research, the esterification reactions of Palm Fatty Acid Disttillate (PFAD) with methanol, using carbon based solid catalyst from coconut shell activated carbon as catalyst, were studied. The ester preparation involved an esterification reaction, followed by purification. In this study, the activated carbon catalyst catalysts were synthesized by sulfonating the activated carbon using concentrated H2SO4. The physico-characteristics and acid site densities were analyzed by Nitrogen gas adsorption, FT-IR, X-ray fluorescent (XRF), and acid-base back titration methods. The effects of the molar ratio of methanol to oil (6:1 to 12:1), the amount of catalyst (1-10%), and the reaction temperature (40, 50 and 60oC) were studied for the conversion of FFA to optimize the reaction conditions. The optimal conditions were an methanol/PFAD molar ratio of 12:1, the amount of catalyst of 10%wt., and reaction temperature of 60oC.

SO3H and NH2+ functional carbon-based solid acid catalyzed transesterification and biodiesel production

A SO3H and NH2+ functional carbon-based solid acid was used as a highly active heterogeneous catalyst for the transesterification of various carboxylic methyl esters with alcohols under mild conditions.

Preparation, Characterization and Catalytic Activity of Alkyl Benzene Sulfonic Acid Carbon-Based Acid Catalyst

Based on starch and series of alkyl benzene sulfonic acid as the materials, a novel carbon-based solid acid catalyst is synthesized using hydrothermal method. This catalyst exhibits much higher catalytic activity in the reaction of esterification of Mono-fatty alcohol polyoxyethylene maleate esters with 1,4-butanediol. The structure of carbon-based solid acid catalyst was charactered by IR and XRD, characterizations showed that this catalyst exhibited high –SO3H loading. Reusability of the carbon-based solid acid catalyst for esterification showed that after recycling five times the activity remained unchanged.

Catalytic Performance of Biomass Carbon-Based Solid Acid Catalyst for Esterification of Free Fatty Acids in Waste Cooking Oil

A series of carbon-based solid acid catalysts were prepared from bagasse using a carbonization–sulfonation method and employed to catalyze esterification of oil with methanol to produce biodiesel. The physical and chemical properties of the biomass carbon catalysts were characterized by FTIR. The pretreatment of bagasse, carbonization temperature, sulfonation temperature and time, as well as the catalytic performance were systematically investigated. The results indicated that the catalysts prepared from bagasse with dilute acid hydrothermal treatment showed the best performance. For the catalysts, the acid value of waste cooking oils was decreased to 1 mg KOH/g, and FFA conversion reached 94.4 % after reaction for 4 h under optimized reaction conditions. The catalysts also showed better stability than traditional homogeneous catalysts.

High activity ordered mesoporous carbon-based solid acid catalyst for the esterification of free fatty acids

Sulfonated mesoporous carbon catalysts were synthesized using a carbonization–sulfonation method and employed to the pre-esterification of free fatty acids contained in high acid value oil. Various synthesis parameters, such as composition of carbon precursor, carbonization and sulfonation temperature, were systematically investigated. The catalysts were characterized by N2 adsorption, small angle XRD, HRTEM, FT-IR and strong acid density analysis. The results indicated that they have a high surface area, uniform pore size, large mesopore volume, high acid density and good catalytic activity. Among them, MC600-S160 exhibited a highest activity and good stability for the esterification of FFA with methanol, the FFA conversion reached 94.6% after reaction for 3h.

Glycerol Valorization as Biofuel Additives by Employing a Carbon-Based Solid Acid Catalyst Derived from Glycerol

A two-step process was developed for the preparation of triacetylglycerol (TAG), a biofuel additive employing a solid acid catalyst derived from glycerol. The first step involves esterification of glycerol with acetic acid (1:4 mol) at 115 °C for 1 h in the presence of catalyst (5 wt %) to obtain 100% conversion of glycerol with 22, 67, and 11% MAG, DAG, and TAG, respectively. In the second step, the esterified product mixture after removal of excess acetic acid and moisture was acetylated with acetic anhydride (1 mol with respect to glycerol) at 115 °C for 30 min to obtain 100% TAG. The recovered catalyst was reused for five cycles without any significant loss of its initial activity. The protocol is cost-effective due to the use of highly stable and recyclable SO3H-carbon catalyst for the production of TAG with minimum moles of acetic acid and acetic anhydride in shorter reaction time.

Influence of reaction conditions on heterogeneous hydrolysis of cellulose over phenolic residue-derived solid acid

A carbon-based solid acid (CSA) was prepared from phenolic residue which is the solid waste generated from the refining of crude phenol. Influence of various reaction conditions on hydrolysis of cellulose over phenolic residue-derived solid acid (PRCSA) is discussed. The results indicate that both cellulose hydrolysis and the effectiveness of PRCSA need a suitable temperature range. The glucose can be adsorbed on the surface of PRCSA due to the hydroxyl-rich structure of PRCSA. The behavior of generated glucose in competitive adsorption with unreacted cellulose on PRCSA suppresses the continuing hydrolysis of cellulose to some extent. For PRCSA, the number of effective active sites increases with the decrease of catalyst particle size. In heterogeneous hydrolysis of cellulose assisted by inorganic salts, the promotion of KCl and NaCl is remarkable, which is attributed to the decrystallization of chloride ions on cellulose and the ion exchange between cations and H+ in –SO3H bonded to PRCSA.

Experimental Study on Cellulose Hydrolysis Using Active Carbon-Based and Carbon Nanotube-Based Solid Acid Catalysts

Three kinds of carbon-based solid acid catalysts were prepared to hydrolyze cellulose with activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs) as the carrier. The prepared solid acid catalysts were characterized by BET, SEM, XRD, FTIR and TG analysis. The catalytic activities of these prepared solid acid catalysts for heterogeneously catalyzed hydrolysis of microcrystalline cellulose were further investigated. The catalysts bearing hydroxyl, carboxyl and sulfonic groups is thermally stable. Due to the amorphous multi-layered structure and the large number of defected structure, AC-based solid acid bears more acid groups than the MWCNTs-based catalyst. which hence showing higher activity for the catalytic hydrolysis of cellulose. AC-based solid acid exihibited two-fold higher catalytic efficiency than that of the MWCNTs-based solid acid catalysts.

Comparison between liquid and solid acids catalysts on reducing sugars conversion from furfural residues via pretreatments

Liquid sulphuric acid is adopted and compared with carbon-based sulfonated solid acids (coal tar-based and active carbon-based) for furfural residues conversion into reducing sugars. The optimum hydrolysis conditions of liquid acid are at 4% of sulphuric acid, 25:1 of liquid and solid ratio, 175°C of reaction temperature and 120min of reaction time. The reducing sugar yields are reached over 60% on liquid acid via NaOH/H2O2, NaOH/microwave and NaOH/ultrasonic pretreatments, whereas only over 30% on solid acids. The TOFs (turnover number frequency) via NaOH/H2O2 pretreatments are 0.093, 0.020 and 0.023h−1 for liquid sulphuric acid, coal tar-based and active carbon-based solid acids catalysts, respectively. Considering the efficiency, cost and environment factors, the liquid and solid acids have their own advantages of potential commercial application values.